Compact RCS Test Range Feed Carousel and Baffle House Design

A new compact range for RCS measurements has been installed and qualified by Orbit/FR Engineering Ltd. MVG. It has a Quiet Zone of 3m diameter, 3m length and operates from 0.7 to 50 GHz, with a feed carousel that allows for fully automated feed change. The RF design is not intended for antenna measurements in its current configuration, but mainly dedicated to RCS. The operational frequency band is split into three sub-bands: each of the lower two bands have a monostatic operated dual polarized feed, while the higher band has a quasi-monostatic operated feed configuration with two dual polarized feeds. Pulsed Tx/Rx modules are directly integrated into the feed assembly. Also, the RF band switching equipment, as well as the network analyzer, are integrated in the feed carousel, so that there are no flexing cables or any other relative movement of RF components when the relevant feed is moved into the focus. Together with tight temperature control, this leads to the best possible RF stability. Since all measurements are time gated, there is no need for an absorber baffle wall to prevent feed direct leakage into the quiet zone. Thus, all feeds are mounted on a clean absorber disk without any absorber blockage and unwanted primary pattern distortion down to a conical angle of 90deg. This allows to obtain an exceptionally good QZ performance even at the lowest frequencies, with an outstanding comparison with the predictions based on Physical Optics. The paper will describe the range design fundamentals, the feed carousel concept and the relevant RF instrumentation. The Quiet Zone performance evaluated by field probing with a Shorted Antenna located in the Quiet Zone will be extensively presented, demonstrating full compliance with the specifications.